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Asthma and Growing Up on a Farm

Dr. Paul Ehrlich

Those of you who get all the alerts about asthma and allergy-related news the way we do were bombarded by a study in the New England Journal of Medicine that seemed to support the Hygiene Hypothesis. In case you’re not familiar with the HH, or as some of us call it, the “pound of dirt theory,” it posits that part of our immune system produces an antigen called IgE, which evolved to fight parasites in unhygienic conditions that have prevailed for most of human history, and since we are now cleaner, in some of us these antigens attack otherwise harmless proteins, making us sick.The findings, based on data from Europe, were summarized as follows:

“Children living on farms were exposed to a wider range of microbes than were children in the reference group, and this exposure explains a substantial fraction of the inverse relation between asthma and growing up on a farm.”

I was asked to appear on short notice on Doctor Radio at New York University School of Medicine to discuss this study, and I did so on February 28th. Half an hour, with phone calls from listeners, was too little to make a dent in this subject, so I’ll elaborate here.

This was a story that resonates deep in American thinking. It evokes the mythic hold that farm life has over our national psyche. Farms good; cities bad. Wholesome Jeffersonian America is not only good for our children morally, but physically. The implication here is that if we would only send the kids to the farm for the first years of their lives, asthma wouldn’t be at the epidemic levels we now have. It’s the Fresh Air Fund in reverse. Send the kids to the country, where the air is full of all kinds of crap. Or maybe we could find ways of bringing the country to the city.

The trouble is that medical science has too many variables to draw sweeping conclusions from one set of data. Anyone who would do so is either very shallow, stupid, or driven by an agenda. A case in point is a Forbes blogger who used the study to take a pot shot at litigation against landlords. To wit, mold is good for us, so dismiss all the suits.

Well, some mold is good. Without mold, we wouldn’t have penicillin or blue cheese. But some mold can kill, particularly stachybotrys chartarum –toxic black mold–which is often found in buildings with water damage. Other molds are potent allergens, including the ones you find in the woods. The smell can be highly obnoxious even to the non-allergic. And let’s face it, landlords can’t decide which molds to allow in their properties.

As luck would have it, I left the NYU studio at 9 AM, returned to my office where I met a new patient with a history of mold sensitivity garnered from a massive exposure of water pouring in from the local electric company’s mistake. I have no idea if he is suing or not.

As objectionable as I find enlisting a specious inference in service of an ideological argument against the American tort bar, there are other things to consider before we let the kids run barefoot through the barnyard.

First, there’s the fact that these were European farms under study, and European farms are regulated very differently from our own, based in part on the health fears of the European commissioners. For example, genetically modified food is much more tightly restricted, if it is legal at all (which is probably pretty irksome to those guys at Forbes). This means that they use different fertilizers and pesticides than the ones we have here.

In any case, rural America is suffering from an asthma epidemic, too. Our guest editorialist David Van Sickle wrote in these pages in November that studies of farm workers in California showed that exposures to agricultural dusts were associated with the development or persistent wheeze, exposure to pesticides was associated with the development of asthma in women, and that community exposures to airborne waste from large scale animal agriculture might also be associated with exacerbations of asthma. Indeed, as he also pointed out, CDC research indicates that asthma is as much an epidemic in rural America as in urban America. It may have remained hidden because it’s hard to study, but that is changing. Throw into that the effects of climate change on the pollen season and other environmental challenges and it’s hard to know whether farms are healthy or not.

If I sound equivocal, it’s because I am. Who knows? Maybe all those farm microbes do have a salutary effect on kids’ immune systems. But how do you prescribe them or administer them to all the millions of children who live in cities?

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